Auto merge of #10895 - mbrubeck:byteindex, r=pcwalton

Use byte indices instead of char indices for text runs

Replace character indices with UTF-8 byte offsets throughout all code dealing with text runs.  This eliminates a lot of complexity when converting from one to the other, and interoperates better with the rest of the Rust ecosystem.

For most code this is just a simple replacement of char indices with byte indices.  In a few places like glyph storage and text fragment scanning, it also lets us get rid of code that existed only to map between bytes and chars.

Also includes some related fixes to text shaping, discovered while working on this conversion.  See the commit messages for details.

r? @pcwalton

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1 files changed, 22 insertions, 19 deletions

diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index 1b828c10e27..74845a1afb9 100644
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -31,22 +31,23 @@ use dom::nodelist::NodeList;
 use dom::validation::Validatable;
 use dom::virtualmethods::VirtualMethods;
 use msg::constellation_msg::ConstellationChan;
-use range::Range;
 use script_runtime::CommonScriptMsg;
 use script_runtime::ScriptThreadEventCategory::InputEvent;
 use script_thread::Runnable;
 use script_traits::ScriptMsg as ConstellationMsg;
 use std::borrow::ToOwned;
 use std::cell::Cell;
+use std::ops::Range;
 use string_cache::Atom;
 use style::element_state::*;
 use textinput::KeyReaction::{DispatchInput, Nothing, RedrawSelection, TriggerDefaultAction};
 use textinput::Lines::Single;
 use textinput::{TextInput, SelectionDirection};
-use util::str::{DOMString, search_index};
+use util::str::{DOMString};
 
 const DEFAULT_SUBMIT_VALUE: &'static str = "Submit";
 const DEFAULT_RESET_VALUE: &'static str = "Reset";
+const PASSWORD_REPLACEMENT_CHAR: char = '●';
 
 #[derive(JSTraceable, PartialEq, Copy, Clone)]
 #[allow(dead_code)]
@@ -174,7 +175,7 @@ pub trait LayoutHTMLInputElementHelpers {
     #[allow(unsafe_code)]
     unsafe fn size_for_layout(self) -> u32;
     #[allow(unsafe_code)]
-    unsafe fn selection_for_layout(self) -> Option<Range<isize>>;
+    unsafe fn selection_for_layout(self) -> Option<Range<usize>>;
     #[allow(unsafe_code)]
     unsafe fn checked_state_for_layout(self) -> bool;
     #[allow(unsafe_code)]
@@ -207,8 +208,7 @@ impl LayoutHTMLInputElementHelpers for LayoutJS<HTMLInputElement> {
             InputType::InputPassword => {
                 let text = get_raw_textinput_value(self);
                 if !text.is_empty() {
-                    // The implementation of selection_for_layout expects a 1:1 mapping of chars.
-                    text.chars().map(|_| '●').collect()
+                    text.chars().map(|_| PASSWORD_REPLACEMENT_CHAR).collect()
                 } else {
                     String::from((*self.unsafe_get()).placeholder.borrow_for_layout().clone())
                 }
@@ -216,7 +216,6 @@ impl LayoutHTMLInputElementHelpers for LayoutJS<HTMLInputElement> {
             _ => {
                 let text = get_raw_textinput_value(self);
                 if !text.is_empty() {
-                    // The implementation of selection_for_layout expects a 1:1 mapping of chars.
                     String::from(text)
                 } else {
                     String::from((*self.unsafe_get()).placeholder.borrow_for_layout().clone())
@@ -233,24 +232,28 @@ impl LayoutHTMLInputElementHelpers for LayoutJS<HTMLInputElement> {
 
     #[allow(unrooted_must_root)]
     #[allow(unsafe_code)]
-    unsafe fn selection_for_layout(self) -> Option<Range<isize>> {
+    unsafe fn selection_for_layout(self) -> Option<Range<usize>> {
         if !(*self.unsafe_get()).upcast::<Element>().focus_state() {
             return None;
         }
 
-        // Use the raw textinput to get the index as long as we use a 1:1 char mapping
-        // in value_for_layout.
-        let raw = match (*self.unsafe_get()).input_type.get() {
-            InputType::InputText |
-            InputType::InputPassword => get_raw_textinput_value(self),
-            _ => return None
-        };
         let textinput = (*self.unsafe_get()).textinput.borrow_for_layout();
-        let selection = textinput.get_absolute_selection_range();
-        let begin_byte = selection.begin();
-        let begin = search_index(begin_byte, raw.char_indices());
-        let length = search_index(selection.length(), raw[begin_byte..].char_indices());
-        Some(Range::new(begin, length))
+
+        match (*self.unsafe_get()).input_type.get() {
+            InputType::InputPassword => {
+                let text = get_raw_textinput_value(self);
+                let sel = textinput.get_absolute_selection_range();
+
+                // Translate indices from the raw value to indices in the replacement value.
+                let char_start = text[.. sel.start].chars().count();
+                let char_end = char_start + text[sel].chars().count();
+
+                let bytes_per_char = PASSWORD_REPLACEMENT_CHAR.len_utf8();
+                Some(char_start * bytes_per_char .. char_end * bytes_per_char)
+            }
+            InputType::InputText => Some(textinput.get_absolute_selection_range()),
+            _ => None
+        }
     }
 
     #[allow(unrooted_must_root)]